"As these medications sit around, maybe a family member has a cough and think, 'oh, my mom has some antibiotic on the shelf, maybe I'll just try that," said Dr. Mark Pregenzer, a pharmacist at Ronald Reagan UCLA Medical Center.

He says many people may try to flush them down the toilet, which may contaminate the water treatment system, or throw them in the trash, where there are similar environmental concerns. But that's not all.

"If somebody really wants... is a medication addict or something and they start searching through trash, that may not stop them," said Pregenzer.

Experts say having excess medications around can contribute to opiate abuse, confusion (especially among the elderly), and antibiotic resistance because you haven't finished your medicine.

"You shouldn't come back to it in a year and think, 'oh maybe I should try this antibiotic for my condition.' You really need to get proper treatment with a physician," said Pregenzer.

He says people should dispose of their unused drugs at designated collection sites.

If you've got a bulging medicine cabinet, the DEA is giving you another opportunity this weekend to properly dispose of some of those medications. This Saturday, April 30, more than 5,000 pharmacies, police stations and other sites will be part of National Prescription Drug Take-Back Day.

"They actually get incinerated, which is actually the best way to dispose of these medications," said Pregenzer.

Last September, Americans turned in about 121 tons of prescription drugs at 4,100 sites across the country.